Classification gage



E. L. GRIGGS CLASSIFICATION GAGE Sept. 2, 1969 4 Sheets-Sheet 1 Filed July 15, 1966 INVENTOR. [AMER L. GR/GGS BY Robzi'chdag MI,

Sept. 2, 1969 E. L. GRIGGS CLASSIFICATION GAGE 4 Sheets-Sheet Filed July 15, 1966 INVENTOR. ELMER L. 62/665 ATTOfNE V Sept. 2, 1969 E. amass CLASSIFICATION GAGE 4 Sheets-Sheet 5 Filed July 15, 1966 INVENTOR. EL M52 L 62/665 ATTOKNE Y Sept. 2, 1969 E. L. amass CLASSIFICATION GAGE 4 Sheets-Sheet 4 Filed July 15, 1966 INVENTOR. ELMM L. 62/665 ATMKA/EY United States Patent Olfice 3,464,119 Patented Sept. 2, 1969 3,464,119 CLASSIFICATION GAGE Elmer L. Griggs, 1720 Toledo, Burlingame, Calif. 94010 Filed July 15, 1966, Ser. No. 565,521 lint. Cl. Gtllb 3/38 U.S. Cl. 33174 4 Claims ABSTRACT OF THE DISCLOSURE A classification gage is provided with a precision jig which holds the structure to be classified in a certain angular relationship. A classifying dial and a tilting plat form are also provided including linkage means connecting the dial and platform to classify each structure relative to a known standard.

This invention relates to a classification gage, and more particularly to a classification gage for determining the relative effective open area in the various stages of turbojet engines. This invention is recognized to measure and be used on guide vanes, turbine blades and/ or other similar structures.

Each stage of a turbojet engine (axial-flow) includes a row of blades which mount in the hub of the rotor and form radial extensions of the hub in the annular space between the hub and the shroud surrounding it. The blades themselves are small airfoils with their mean chord aligned slightly off the axis of the rotor. When the hub carrying the blades is rotated, it forces air to flow axially through the annular spaces between the hub and the shroud in the compressor stages. The blades are reactive elements driving the hub and rotor when the hot gas from the combustion chamber passes through the corresponding annular space in the turbine stages containing the blades.

Adjacent to each row of blades is a set of stationary guide vanes. Unlike the blades which reflect the hot gas passing therethrough, the purpose of the guide vanes is to change the direction of the air emerging from one row of blades to the subsequent row of blades to insure efficient operation. The correct amount of back pressure must be maintained in each succeeding stage.

The first set of guide vanes in the front of the turbojet engine encounters regular air. The second set of guide vanes has the same amount of air in a proportionally smaller area. As the air goes through each stage, the pressure and velocity increase but the amount of air remains constant. After fuel injection, the reverse process occurs in the turbine wheels; the relative effective open area increases in each succeeding stage.

Determining the actual design for a guide vane, turbine blade or similar structure for each stage is a complicated procedure not readily lending itself to a simple explanation. Two of the better known methods are the twodimensional cascade with prescribed velocities along the blade surface for compressible gas flow, and the channeltype method which takes into account the spacing between the various blade elements in the row after the blade element profile has been designed for prescribed gas velocities across it.

Whether either of the two methods mentioned above or any alternative technique is used, the final parameters will include a certain effective open area in the row of guide vanes for the passage of the gas therethrough. This total open area in the row of guide vanes is very important and in an average size turbojet engine must not vary more than one square inch from the parameters determined. If the area is too small choke-off may occur and the desired quantity of fluid cannot be passed through this stage.

Recognizing the necessity of close control in the effective open area in the rows of guide vanes, it is important to have accurate means for determining the effective open area in the rows of guide vanes. Since the mean chords of the guide vanes are slightly off-set, their trailing edges being toward the rear of the engine, some of their surface area of each is blocked by the frontal portions of the guide vanes so that effective open area in the row of guide vanes will depend on their actual angular relationship with the axis of the rotor, their length and the blocked area of each of the guide vanes. Further, it is desirable that the small open areas between adjacent guide vanes which contribute to the total open area be kept as uniform as possible throughout the circular row of guide vanes. This means that the mass produced guide vanes for new engines and/ or the guide vanes in turbojet engines being rebuilt must be more or less matched to give the desired effective open area and maintain uniformity of areas between adjacent guide vanes.

To obtain accurate control of the effective open area a class or vane category system has been set up by various manufacturers. This class system is a category of parts by number and will be discussed in greater detail hereinafter. The classification gage of this invention integrates a plurality of dimensions into one gage reading.

The primary object of this invention is to provide a new and improved classification gage.

Another object of this invention is to provide a precision classification gage for classifying guide vanes or the like of turboget engines so that they may be assembled to give the proper effective open area.

Another object of the present invention is to provide a precision gage which correlates both the guide vane angle and the guide vane length to calculate the proper guide vane classification.

A further object is to provide an accurate classifier gage for the turbojet guide vanes which is relatively simple in design and construction.

A still further object is to provide a precision classifying gage which can save many man-hours in establishing the proper open area in a row of guide vanes in a stage of a turbojet engine while maintaining precision accuracy.

Other objects, features and advantages of the present invention will be apparent from the following description of a preferred embodiment illustrated in the accompanying drawings in which:

FIGURE 1 is a perspective view of the novel classifying gage of the present invention illustrating the precision jig and the direct reading dial assembly;

FIGURE 2 is a perspective view of a typical guide vane used in a turbojet engine;

FIGURE 3 is a cross-sectional view of a portion of the row of guide vanes, like the guide vane shown in FIGURE 2, installed in a stage of a turbojet engine;

FIGURE 4 is a perspective view partially in section illustrating a gage standardization or calibration block which is machined to give the desired readings for a particular class of guide vanes to be measured by the gage;

FIGURE 5 is a top plan view of the guide vane classifier gage of this invention with various parts broken away to show the internal detail;

FIGURE 6 is a side elevational view of the gage with a guide vane shown in cross-section positioned in the precision jig of the gage;

FIGURE 7 is a schematic diagram of the movable parts of the precision jig of the gage showing the internal relationship of the parts and also showing the tiltable platform and its connection to the direct reading dial;

FIGURE 8 is a vertical cross-sectional view through the gage taken substantially as indicated along line 8-8 of FIGURE 5, with parts broken away;

FIGURE 9 is a vertical sectional view with parts broken away taken substantially as indicated along line 99 of FIGURE 8 showing part of the aligning mechanism cooperating with the anvil;

FIGURE 10 is a vertical sectional view taken substantially as indicated along line 1010 of FIGURE 8 showing the contacting mechanism for the convex portion of the guide vane; and

FIGURE 11 is a horizontal sectional view taken substantially as indicated along line 1111 of FIGURE 8 showing the aligning mechanism cooperating with the anvil for receiving the trailing edge of the guide vane.

In accordance with the present invention, a classification gage is provided with a precision jig which holds the airfoil portion of the guide vane in a certain angular relationship depending on the length of the guide vane and a tilting platform for receiving the lug or buttress on the root of the guide vane and a classifying dial and linkage means connecting the platform with the dial so that the guide vane in the jig may be classified relative to a known standard with which the gage is calibrated by the inclination of the platform caused by the impingement of the lug or buttress thereon moving the dial through the linkage means.

The precision jig is itself unique having an anvil for receiving the trailing edge of the airfoil section of the guide vane, a cooperating aligning means which orient the trailing edge of the guide vane on the anvil, a selfaligning contact means for contacting the convex surface of the guide vane, a linkage means connected to the contact means, wedging means connected to the linkage means, and pivoted arms associated with the wedging means which are forced outwardly by the wedging means as the contact means are depressed by the guide vane until the arm is stopped by the inside surfaces of the mounting lugs on the root and tip of the guide vane at which time the position of the guide vane in the jig is fixed. Once the position of the guide vane is fixed in the jig, the tiltable platform will have a certain inclination as a result of impingement of the guide vanes lug which will read on the dial as a class number since the gage has been previously set with a standard. Thus, the gage will determine if the guide vane is the same as the standard or will have a greater or lesser open area when installed in the engine than would the standard guide vane in that particular class.

To understand the operation of the novel gage shown in FIGURE 1, some attention must be given to the structure to be classified. This may be either a guide vane, a turbo blade or some other similar structure. For the purpose of this specification, and not in any way to limit the claims, a guide vane will be taken as a typical example. A typical turbojet guide vane, generally indicated 20, is shown in FIGURE 2 having a central section 21 which is shaped in a form of an airfoil, a hub mounting flange or lug 22 attached to or integral with the root 23 of the guide vane and rim mounting lug or flange 24 at the tip 25 of the guide vane. A series of guide vanes are shown as they would be mounted in a turbojet engine in FIGURE 3 and the distinct airfoil characteristic of the central section 21 can be seen, which are shown in section for this purpose.

For the most part the airfoil of the central section 21 of each guide vane 20 is uniform and the two principal factors to be considered in determining the open area in the set of guide vanes is the angle the central section 21 makes with its hub mounting flange or lug 22 and the length of this section. As can be seen in FIGURE 3, if the central section 21 is rotated on the face of hub mounting lug 22, it will change the open area between such a guide vane and its two adjacent guide vanes in the row. Further, the actual change in the open area will be dependent on the length of the central blade section 21, i.e., the distance between the inside surfaces of the tip and hub mounting lugs or flanges, 24 and 22 respectively. In addition, even though the aerodynamic profile of the section 21 is known, part of the area of the guide vane on the trailing edge 26 is blocked by other parts of the guide vane and this must be considered. This blocked area B is shown in FIGURE 3 between parallel lines 27.

Since it is possible to determine the amount of effective open area needed in a particular set of guide vanes and also the vanes airfoil profile, it is then possible to determine, knowing the number of vanes in the set, the angle that each vane should be set on the mounting lug 22 and the length of each airfoil section which will give uniform spacing between the vane and which will add up to the total desired open area required in the particular set of guide vanes in a particular stage of the turbojet engine. This determination represents the ideal vane for the set. Using this information it is possible to manufacture a standardization of calibration block 30 (shown in FIGURE 4) for the novel classification gage of this invention by which the gage can be set and guide vanes mass produced and/or vanes of turbojet engines being overhauled can be compared relative to the standard or ideal vane for the set in question.

Calibration block, generally indicated 30, is provided with carbide or other non-wearing elements where the gage will contact the block so there will be little wear when the gage is standardized. Basically, the block is contacted by the gage in four places. The first is the thin edge 31 which corresponds to the extreme trailing edge 26 of the central vane section 21. The second point of contact on a vane by the gage is the convex outer portion of the central blade section 21 at the point from which the trailing edge portion of the blade is blocked which is a distance D up from the trailing edge of the blade, as can be seen in FIGURE 3. A carbide bar 32 is located on the block 30 in a point which corresponds with the point the actual vane would be contacted and milled to the exact relationship that would exist in the actual ideal vane. The distances represented by letters in FIGURE 3 are shown as the prime letters in FIGURE 4 for corresponding distances. This third point of contact of the gage with a vane is length correlation points, and the block 30 is provided with two carbide buttons 33 and the distance therebetween is the length of the ideal vane for a particular stage of the engine. The last point of contact with the actual vane by the gage is the base 28 of the hub mounting lug or flange 22 adjacent to the trailing edge 26 of the central section 21. To provide for this contact the block 30 is provided with two end plates 34 which hold the carbide buttons 33 previously mentioned. One of the end plates 34, that which corresponds with lug 22 of the actual vane has two carbide pads 35 mounted on its edge where the gage will contact it.

By milling the standardization or calibration block 30 so that the contact points thereon are in the same special relationship as would be these points in an actual ideal vane it is possible to use this block to standardize the gage anytime this becomes necessary.

Of course, once the gage is standardized with block 30 actual vanes may be compared in the gage to determine how they vary relative to the ideal or standard vane. This is usually done by setting the dial of the gage to a certain class number with the block 30 in the gage and classifying other vanes relative thereto in the gage by reading directly from the dial. Some vanes will read as the same class, some will be over and some will be under. If the differences between the classes are known, vanes from diflerent classes may be combined in the set to achieve the exact open area required for that set. Thus, through the use of the gage it is possible to save hours of labor to build and/or rebuild better turbojet engines.

The overall appearances of the novel classification gage generally indicated 40, of this invention can be seen in FIGURE 1 where it is apparent that it has two principal parts. The first and largest principal part is the precision jig, generally indicated 41, for receiving and holding the vanes 20 in a particular special relationship depending on their dimensions and the second principal part is the dial assembly, generally indicated 42, which is fastened on one side of jig 41.

The precision jig 41 is the largest and most complicated part of gage 40. Its support member is a large, flat base block 43 which is generally a rectangular box shape. On this base block all other parts of the gage are mounted. On the top fiat face 44 of the base block 43 two vane aligning assemblies are mounted which are designed to precisely position a vane being classified Within the precision jig 41.

The smaller of the blade aligning assemblies is the vane trailing edge guide 45. This trailing edge guide 45 has an anvil support structure 46 which has a carbide anvil 47 (FIGURE 8) mounted on the top thereof on which the trailing edge 26 of the vane 20 will rest when the gage is classifying vanes. Using the hard carbide for the anvil prevents the anvil from wearing significantly and insures long and continuous reliability.

The length of anvil 47 is slightly shorter than the central section 21 of the vanes 20 so that the trailing edge 26 will rest on the anvil for the greater part of its length. Since the anvil 47 has a fiat top surface on which the trailing edge 26 of each vane will rest it is necessary to precisely position the trailing edge on the anvil if an accurate classification of a vane placed in the gage is to be obtained.

To position the trailing edge 26 of a vane being classified, or for that matter the carbide edge 31 of the standardization block 30, on the top fiat surface of anvil 47, the trailing edge guide 45 has a plurality of stop rods 48 (FIGURES 5 and 8) which are mounted in a housing structure 49 contiguous to the anvil support structure 46 so they will project out of the housing structure in a plane parallel to the top face of the anvil. In the embodiment of jig 41 shown in the drawings the stop rods 48 are positioned in the housing structure 49 so that the central axis of each rod is parallel to those of the other rods and also coplanar with the top flat surface of the anvil 47. Thus, when the stop rods 48 are moved toward the anvil, half of the circular rod ends will be above the top surface of the anvil. Notches are provided in the anvil 47 so that the ends of the stop rods 48 will be in the middle portion of the anvil when properly positioned and so that parts of the anvil on either side of the rod ends will support the trailing edge. Thus, the trailing edge 26 of a vane can be rested on the anvil 47 and pushed across the top of the anvil until it engages the semicircular projecting portion of the stop rods 48 at which time it is positioned on the face of the anvil 47.

Stop rods 48 are all the same length and are free to reciprocate in and out of the housing structure 49. The purpose of the stop rods rather than mechanical stops fixed on the surface of the anvil is to take a mechanical average of the trailing edge of the vane resting across the face of the anvil 47 and this average can be used to position this part of the vane in the precision jig 41. The mechanical average of the trailing edge 26 of a vane is obtained by a mechanical averaging linkage, generally indicated 50, shown schematically in FIGURE 7 along the right side.

Mechanical averaging linkage 50 can also be seen clearly in FIGURE 5 where parts have been broken away to show this detail. Referring to the schematic in FIG- URE 7 the inboard ends of stop rods 48 are represented by circles 48a in the averaging mechanism. Since the rods are all the same length they will be pushed back uniformly by the trailing edge of the vane until they are stopped by the averaging mechanism 50 as will be appreciated by studying the schematic which will show that it forms an averaging stop for the inboard rod ends.

More specifically, this is accomplished by a series of pivots wherein pairs of adjacent rods 48 are averaged through a pivot 51, and then an average of the two rods are averaged with the average of the two other rods through a second pivot 52, and thereafter this composite average is averaged with a composite average obtained in the same manner but on a different portion of the blade edge through a third pivot 53 which is anchored to the housing structure 49. All the pivots of the averaging mechanism are free-swinging pivots with the exception of the third pivot 53. Thus looking at the averaging mechanism 50, shown in the schematic in FIGURE 7 and which is composed of two identical parts as described above, the guide vane edge inserted in the jig and resting on the anvil 47 when pushed into the rod ends will have its edge mechanically averaged in the jig. This means that any irregularities in the trailing edge of the guide vane edge are averaged out so that the classification of the vane placed in the jig will be more accurate.

The basic unit of the averaging mechanism 50 is a crank 54 (FIGURES 9 and 11) having flat parallel surfaces 57 for receiving the inboard end of rods 48 equidistant from the pivot 51. The cranks 54 are shaped so that they will not turn over under any pressure conditions. As the rods are of equal length the two rods connected through crank 54 will average their respective points of contact on the trailing edge 26 of a guide vane placed in the jig 40. As can be seen in FIGURE 9 each two adjacent cranks 54 are connected through their respective pivots 51 through a gimbal '55 which is in turn pivoted on one of the arms of the main gimbal 56 through pivot 52. Thus in the embodiment shown in the drawings the contact points of the eight stop rods 48 are averaged in the assembly and two of these assemblies are used across the total length of the trailing edge of a guide vane placed in the jig 41. This gives the average of 16 points on the trailing edge 26 of each of the vanes placed in the jig to more accurately position the vane on the anvil 47 Another general area where the guide vanes inserted into the precision jig 41 are contacted to position them properly within the jig is the convex surface of the vanes at a point preferably where the blocked area begins, a distance D up from the trailing edge of the blade as discussed earlier. This general area is on the opposite side of the vane than that contacted by the stop rods 48 and is located above the anvil 47. Since this contact point of the jig with the vane in the jig is above the anvil 47 a vane inserted in the jig can have its trailing edge placed on the anvil and then pulled toward the jigs contacts in this area to properly position the vane and force the trailing edge of the vanes into the projecting ends of stop rods 48.

For contacting the vanes in the jig 41 on their convex surface above the trailing edge, a mechanical averaging assembly 60 similar to assembly 50 used on the trailing edge of the vane is employed. As can be seen on the left side of the schematic shown in FIGURE 7 there is a great deal of similarity between these assemblies. Instead of using the stop rods 48 to give a plurality of points on the vane, averaging unit 60 uses pairs of carbide balls 61 mounted in pads 62 which are in turn pivoted on a gimbal 63 which holds two pads through pivots 64 between the pads 62 and the gimbal 63. In turn each of the gimbals 63 is pivoted through pivot 65 to the main gimbal 66 on one of the latters arms.

As can be seen from the drawings, averaging unit 60 has eight contact points across the convex side of a vane positioned on the anvil 47 and when the vane is pulled into the contacting balls 61 the trailing edge of the vane will be forced into the protruding ends of the stop rods 48 until the vane is properly positioned. The operation of the averaging unit 60 is the same as that of 50 except the main gimbal 66 of the former is not anchored to its supporting housing 67. Instead main gimbal 66 is, through pivot 68, connected to a reciprocating piston assembly 69 which moves back and forth generally perpendicular to the row of contacting balls 61 on this averaging unit 60. Thus when the convex surface of a vane inserted into the jig is drawn against balls 61, the piston assembly 69 is pushed back into the supporting housing 67 until the piston assembly is restrained. To restrict the travel of the piston assembly 69 into the housing before the convex surface of the vane hits the housing a wedging bar 70 is pivoted on the piston assembly. Both ends of the wedging bar 70 are tapered as at 70a and the bar is oriented transversely to the back and forth movement of the piston assembly. The specific angle of taper is dictated by a complicated classification formula, which formula is difficult for each set of guide vanes in an engine. The tapered ends of the bar 70a have tracking rollers 71 bearing on their tapers in a manner which will cause the rollers 71 at each end of the wedging bar 70 to be forced apart as the piston assembly is forced into the supporting housing 67. This can be seen in FIGURE of the gage and also viewed in principle in the schematic view shown in FIG- URE 7.

It should be kept in mind that the averaging mechanisms 50 and 60 can be manufactured to have a special effect, if desired, by having an unequal mechanism. Thus, one contact point could be 50% of the average, another 20% and so on. In averaging mechanism 50, for example, each of the 16 contact points contributes equally to the average. However, this need not necessarily always be the case. The type of structure to be classified determines the arrangement of the specific averaging mechanism.

Basically, the tracking rollers are forced apart by the inward movement of the wedging bar 70 because they are mounted on arms 72 which have one end pivoted in the supporting housing 67, so that the movement of the piston assembly 69 into the housing, will cause the arms located on either end of the wedging bar 70 to swing outwardly on either side of the precision jig 41. Thus, by placing carbide contacts 73 on the swinging ends of arms 72 it is possible to bring in the length of each vanes central section 21 if these contacts 73 contact the inside surfaces of the mounting lug 24 and the mounting lug 22.

From the above discussion it should be apparent that the travel of the piston assembly 69 into the supporting housing 67 will be directly proportional to the length of the central section 21 of each vane placed in the jig 41 and pulled back against the carbide balls 61 contacting the convex surface of the vanes central section, since the piston assemblys movement is limited, through the wedging bar 70 and its associated arms 72 which are stopped by the inside surfaces of the mounting flanges, 24 and 22 respectively. It is very important that the length of the vanes central section 21 which effects the amount of open area be considered if a proper classification is to be had. Thus, through the use of the above assemblies in the precision jig 41 the length of the central section 21 (i.e., the distance between the mounting lugs) changes the angular position of the blade in the jig in direct proportion to its length.

It should be further appreciated that the guide vanes classified in the gage 40 will have a fairly standard profile which has been determined by the design parameters for the particular stage of the turbojet engine. Thus, the position each vane assumes in the jig is dependent on the length of its central section and its general profile. In order to have each vane held firmly in the jig a weight 80 (FIGURE 6) is attached to the nose of each vane classified when the reading is taken so that each reading is taken under the same conditions. The weight 80 is notched to accept the nose of the vane and its moment is located so that it rocks the convex surface of the vane into the carbide contacts 61 of the jig.

Thus any vane placed in the jig 41 assumes a particular position depending on the characteristics of that particular vane. This position is the characteristic position for that vane, and each vane, as well as the standardization block 30 which is used to set the gage, has its own characteristic position in the jig. The complicated formulas for determining the actual change in angular position for each unit of length of variation from the standard, need not be considered to understand the operation of the gage. It is however, important to recognize that all these factors are considered in the angular position that the vane assumes when placed in the precision jig 41.

Recognizing that every vane placed in the precision jig 41 has a characteristic position, it is necessary to convert this information into a useful classification number. This is accomplished by the second major part of the gage, the dial assembly generally indicated 42. The dial assembly is able to do this because the orientation of each vane in the set of a particular stage of the turbojet engine is determined by the mounting of the vane on its mounting lug or flange 22. Thus by measuring the characteristic position of the guide vane relative to its lug or flange 24 a useful classification can be made when the reading has been standardized with block 30.

To utilize this principle the gage of the invention utilizes one of the surfaces of the mounting lug or flange 22 of each vane that has a known orientation in the eugine to read a classification therefrom. Since the gage has been set with a known, accurate standard, it is possible to read the classification of each vane put into the gage relative to the standard.

As mentioned before, the surface or side 28 (FIG- URE 2) of the mounting lu-g or flange 22 is the one from which measurements for classification are taken. It can then be appreciated that the position of this side of the lug or flange each vane will determine how the vanes central section 21 will be located in the set of vanes in the engine. Thus by positioning the central Section 21 in a precision jig 41 according to its characteristics, it is possible to classify the vane by the angle side 28 makes relative to a known standard with which the gage 40 has been set.

To get a comparison between guide vanes of unknown classification and the standard the dial assembly 42 uses a system of lever arms as can be seen diagrammatically in FIGURE 7, and in the embodiment of the drawings, it can best be seen in FIGURE 1. The main arm of the system is fixedly pivoted about pin 91 in the housing 92 with which the dial assembly 42 is mounted on the base block 43 of the jig where the end of the vane having lug or flange 22 will be projecting from jig 41 so that an angular measurement can be made on side 28 of the lug or flange. Connected to and carried by the main arm 90 are three other arms which are pivoted on the main arm in the parallel system having pin 91 as one of the pivot points for the system.

As can be seen in FIGURE 7 of the drawings, it would be possible to move this parallel system about pin 91 without changing the position of the dial arm 93 relative to the plunger 94 of dial 95, if the platform arm 96 is kept parallel to its original position because of the parallel linkage of the main arm 90 and the drag arm 97. Therefore, it can be appreciated that by rigidly connecting a platform 98 to the platform arm 96 that the position taken by the platform will determine the position of the platform arm and dial arm 93 of the system which will in turn move the indicator 100 of dial 95.

Thus, if the platform is positioned by the mounting of the dial assembly 42 on the precision jig 41 so that the side 28 on the lugs 24 of the vanes placed in the jig 41 will rest on the platform and orient the platform in the parallel system, the indicator 100 of the dial will move accordingly depending on the position of the platform and give a guide vane classification relative to the standard use to set gage 40. Springs 99 are used on one end of the main arm 90, on the end opposite platform 98, to urge the platform up against the side 28 of the vane being classified so that an accurate reading can be obtained.

The classification index selected for the readings of the dial 95 may be purely arbitrary since the principle is to get a comparison with a known standard and it is only necessary to determine how the unknown vanes vary relative thereto. It is important, however, to know the degree of variation between different classes so that different classes can be used to get the proper open area in a set of guide vanes. For example, if the set calls for class ten vanes, it may be possible to use an equal number of class nine and class eleven vanes for the set, or any intermixture of tens, nines, and elevens so that the average is ten in the resulting set.

The broken line represents a vane 20 shown positioned in the gage as it would be during classification in FIG- URE and contacts of the jigs parts on the vane can be clearly seen. Further all parts of the jig contacting the blades should be made of wear resistant material so that the gage will not develop errors due to wear. Carbide has been found an acceptable material for these contact points.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, for some modifications will be obvious to those skilled in the art.

I claim:

1. A classification gage for a structure having a central section, a length and a hub mounting flange Which integrates a plurality of dimensions of said structure into one gage reading comprising:

(a) a precision jig adapted to receive said structure which includes means to angularly position said structure in said jig in accordance with said length and the contour of said central section;

(-b) tilting means mounted on said jig for contacting said flange of 'said structure when it is held by said jig, said tilting means oriented by the contacted surface of said flange of said structure;

(c) indicating means mounted on said jig to visually show said structure classification; and

(d) linkage means connecting said indicating means and said tilting means which will cause said indicating means to register a classification depending on the position of said tilting means.

2. A classification gage according to claim 1 wherein the precision jig has a plurality of contact points for bolding the structure therein which are capable of averaging out irregularities in said structure surface.

3. A classification gage according to claim 1 wherein the precision jig has structure contact means, arms and wedging means connected to said contact means and operable to force said arms against the inside surface of mounting lugs on said structure to correlate the structure length with its position.

4. A classification gage for a structure having a trailing edge, a convex surface, a length and a hub mounting flange comprising:

(a) an anvil and cooperating aligning means for receiving and orienting said trailing edge;

(b) a self-aligning contact means for contacting said convex surface;

(c) a linkage means connected to the contact means;

(d) wedging means connected to the linkage means;

(e) pivoted arms moved into contact with said structure by said wedging means which position the structure in the :gage in accordance with the length of said structure;

(f) and indicating means responsive to the position of said structure in the gage to visually show a gage reading indicative of said convex surface and length.

References Cited UNITED STATES PATENTS 2,525,267 10/1950 Muzzey et a1.

SAMUEL S. MATTHEWS, Primary Examiner 

